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2nd Partition on 5TB RAID 5 Array running W2K3

Posted on 2011-03-08
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Last Modified: 2012-08-14
I have a Dell PowerEdge 2950 that has a RAID 5 array that totals just under 5TB, during install of W2K3 I created a C: partition of 1.9TB and left the rest unpartitioned. Now that the systems up and running I want to make a D: partition from the remaining unallocated space but the option is grayed out. I know that windows can't boot from a partition larger than 2TB but I don't understand why I can't make a second partition from the remaining space.
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Question by:Dalexan
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by:wantabe2
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Go into computer managment & create the partition there. You should be able to create it & format it from there.
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by:Dalexan
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I believe that's where I'm trying to create the partition at

R-click "My Computer" -> manage -> Disk Management

Then on disk 0 I have the C: partition and an unallocated 2.6GB space. When I R-click the unallocated space the option New Partition is grayed out.
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by:Dalexan
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Err that an unallocated 2.6 TB not GB
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by:PowerEdgeTech
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Windows cannot boot to a >2TB partition**.
Windows cannot see a >2TB partition unless the disk is converted to GPT.
Windows cannot boot to a GPT partition**.

** Unless 2008x64 or greater, installed on EFI-enabled server.  2950 is not EFI-capable.

So, your only two options are:

1) Create two RAID 5's across the disks ... one small enough (<2TB) for your OS to boot to, and the other can be as big as you want.  The second RAID 5 will show in Disk Management as a second "disk", which can then be converted to GPT for partition sizes larger than 2TB.

2) Break up the disks into smaller arrays ... for example, 2 disks in RAID 1 and 3 in RAID 5, etc.  You will sacrifice a disk's worth of space (at least) this way though.
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by:PowerEdgeTech
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Sorry ... I meant to summarize by saying there is no easy way to use the entire space at this point, as you can't "remove" drives from your existing RAID 5.  In either situation, you would be doing a complete backup and restore.
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by:dlethe
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It is not a partitioning problem, it is a LUN/device limit.    I.e, if you have a single physical disk drive, then that is one target device.  If you partition it into C & D, then you still have a single target device, but it is partitioned into 2 LUNs, or volumes or logical devices.

On the RAID you have same thing, you effectively made a 5TB physical disk drive (as seen by the O/S).  By partitioning it, you still have a 5TB device you split into C &D.  That is no good. The 32-bit limit of FFFFFFFFh blocks is the most that can be used with this O/S (which is 2.09 TB when FFFFFFFF hex is multiplied by 512)

You need to create 2 different SCSI IDs with the RAID,  a C disk and a D disk, not a partitioned C drive.  Some controllers will let you partition (at the RAID level) a single RAID set into multiple targets.  

W/o looking up the specs, don't know if this one will, but chances are it will not.  You'll just have to create a single RAID1 with 2 disks, and make that C, and then use the other disks for the D drive
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by:Dalexan
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So far only the OS is on there so I'd just start over from scratch. With that in mind I have 6 x 1TB drives I need at least a 500GB W2k3 boot partition, the rest can be a different partition, all in RAID 5. If I start over can I make 1 array with 84 GB from each disk and the rest in a 2nd array or will I have to split it 3 and 3 ending up with about 4TB total to have all of it in RAID 5?
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by:Dalexan
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ok I see I can't use part of the a disk its all or nothing so 1 RAID 1 array of 2 disks and 1 RAID 5 of 3 disks

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dlethe earned 80 total points
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so go with a 1 TB RAID1 for C, then a 3+1 RAID5 for E.  

Look at specs for the controller (or the configurator ...)   Does it let you PARTITION a logical device in the RAID itself?  I.e, build a big RAID5 and slice it up into pieces and assign ID numbers to each of them?   IF yes, then what you want to do will work.

But even if it did let you, then at least from performance perspective it would be bad.   EVERY I/O on EVERY device will compete with EVERY I/O on every device.  Do so much as change the date of any file on the computer and EVERY drive on the computer will be required to do at least one I/O.

For performance, go with a RAID1 for C, the rest a RAID5.   Optimize the RAID5 for 64KB block size as this is native SQL server I/O size.   The RAID1 device will be at least 2 x faster on any write, perhaps 4x faster, so use C for any scratch files, indexes, log files and the O/S.    Put all the read intensive I/O on the RAID5.   This tunes the I/O to match the performance strengths and weaknesses inherent in the RAID levels.

Google win2k align partitions also, be sure to set that up as well.
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by:Dalexan
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OK I went with the RAID 1 and RAID 5 setup and Googled win2k align partitions and found

http://blog.bennett-scharf.com/2008/03/31/using-diskpart-to-align-a-windows-disk-partition/

and

http://blogs.msdn.com/b/jimmymay/archive/2008/10/14/disk-partition-alignment-for-sql-server-slide-deck.aspx

Is this something that needs to be done during OS install or can it be done after OS install?
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by:PowerEdgeTech
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On a 2950, I would assume you are using a PERC 5 or 6, which will both support "slicing" - or creating multiple arrays across the same set of disks - if you want to go that route.  When creating the array in CTRL-R, specify the size you want the first array to be, then later you can create an array with the remaining space.
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by:Dalexan
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Its a PERC 5/i controller but I've already went with the RAID 1 and RAID 5 arrays
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by:PowerEdgeTech
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It's better that way, but since I missed the discussion, I thought I'd throw that out there for information's sake.
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by:dlethe
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Personally I do it before when convenient, but you have to be able to boot that system first.  If you have a USB-attached windows disk with the RAID drivers, then do formatting / partitioning on NTFS first.  Then installation will go a little faste
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by:Dalexan
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I'll have to do the alignment after I get the OS installed, thanks for all the help going to close that and split the points between the two of you.
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by:PowerEdgeTech
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Good luck.
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